A phosphate of an organic hydroxy compound (hereinafter referred to simply as “phosphate”) is used in fields such as detergents, emulsions, fiber-treating agents, rust preventives and medical supplies. Particularly, an alkali salt metal such as a sodium or potassium monoalkyl phosphate having a long-chain alkyl group, and an alkanol amine salt such as triethanol amine, are water-soluble and excellent in foaming power and detergency with less toxicity and less skin simulation, and are thus useful in commodities applied directly onto the human body, such as shampoos and facial washes. When such commodities applied directly to the human body are compounded with phosphates, it is important for qualities that the phosphates have less color and less smell.
The phosphates can be produced by reacting an organic hydroxy compound with a phosphorylating agent such as orthophosphoric acid, polyphosphoric acid and phosphorus pentaoxide. In the reaction of the phosphorylating agent with the organic hydroxy compound, however, significant coloration occurs and a smell different from that of the starting organic hydroxy compound is generated. Accordingly, troublesome steps for removing coloring components and smelling components are necessary after the phosphorylation reaction.
As a method of removing coloring components and smelling components, there is proposed a method of separating a phosphate by re-crystallization using a solvent (JP-A 11-158193) or a method which includes converting a phosphate with a basic compound into a phosphate salt and then using a solvent to extract smelling components into an organic layer and the phosphate salt into an aqueous layer (JP-B 3-27558).
As a method of preventing coloration in the phosphorylation reaction, there is proposed a method which includes adding a borohydride compound (JP-B 60-43076) or a method which includes adding phosphorous acid, hypophosphorous acid or the like (JP-B 38-12524).
As a method of deodorization without using a solvent, on the other hand, there is proposed a method which includes contacting with an inert gas such as water vapor in a thin-film deodorization column such as a rotary thin-film evaporator and a wetted-walled column (JP-B 62-25155) or a method wherein phosphorylation reaction is carried out while water vapor is blown in (JP-B 5-66958).